Image Resizing

UIImage+Helpers.m

@implementation UIImage (Helpers)
- (UIImage *)scaleImageToSize:(CGSize)newSize
{
    UIGraphicsImageRenderer *renderer = [[UIGraphicsImageRenderer alloc] initWithSize:newSize];
    UIImage *image = [renderer imageWithActions:^(UIGraphicsImageRendererContext*_Nonnull myContext) {
        [self drawInRect:(CGRect) {.origin = CGPointZero, .size = newSize}];
    }];
    return image;
}

+ (UIImage *)scaleImageData:(NSData *)imageData toMaxPixelSize:(CGFloat)maxPixelSize
{
    CGImageSourceRef imageSourceRef = CGImageSourceCreateWithData((__bridge CFDataRef)imageData, NULL);
    CGImageRef imageRef = CGImageSourceCreateImageAtIndex(imageSourceRef, 0, NULL);
    UIImage *scaledImage = [UIImage scaleImage:imageRef toMaxPixelSize:maxPixelSize];
    CGImageRelease(imageRef);
    if (imageSourceRef != NULL) {
        CFRelease(imageSourceRef);
    }
    return scaledImage;
}

+ (UIImage *)scaleImage:(CGImageRef)cgImage toMaxPixelSize:(CGFloat)maxPixelSize
{
    size_t imageWidth = CGImageGetWidth(cgImage);
    size_t imageHeight = CGImageGetHeight(cgImage);
    CGSize scaledSize = CGSizeMake(imageWidth, imageHeight);
    if (imageWidth > maxPixelSize || imageHeight > maxPixelSize) {
        size_t targetWidth, targetHeight;
        if (imageWidth > imageHeight) {
            targetWidth = maxPixelSize;
            targetHeight = (maxPixelSize * imageHeight + imageWidth / 2) / imageWidth;
        } else {
            targetHeight = maxPixelSize;
            targetWidth = (maxPixelSize * imageWidth + imageHeight / 2) / imageHeight;
        }
        scaledSize = CGSizeMake(targetWidth, targetHeight);
    }

    size_t width = scaledSize.width, height = scaledSize.height;

    UIImage *newImage;
    if (imageWidth != width || imageHeight != height) {
        CGColorSpaceRef colorspace = CGImageGetColorSpace(cgImage);
        CGContextRef context =
            CGBitmapContextCreate(NULL, width, height, CGImageGetBitsPerComponent(cgImage),
                                  CGImageGetBytesPerRow(cgImage), colorspace, CGImageGetAlphaInfo(cgImage));
        if (context == NULL) {
            return nil;
        }
        CGContextDrawImage(context, CGRectMake(0, 0, width, height), cgImage);
        CGImageRef imageRef = CGBitmapContextCreateImage(context);
        newImage = [UIImage imageWithCGImage:imageRef scale:1 orientation:UIImageOrientationRight];
        CFRelease(imageRef);
        CGContextRelease(context);
    } else {
        newImage = [UIImage imageWithCGImage:cgImage scale:1 orientation:UIImageOrientationRight];
    }
    return newImage;
}
@end